A Corylus avellana L. extract enhances human macrophage bactericidal response against Staphylococcus aureus by increasing the expression of anti-inflammatory and iron metabolism genes

[Display omitted] •This study improves the knowledge on hazelnut biomolecules composition (71).•The host inflammatory state influences the effectiveness of C. avellana extract (80).•An association between plasma-LDL, inflammation and innate immunity is proposed (79 car). Corylus avellana L. is known for its healthy properties, and yet previous studies have not dealt with its effects on human innate response. The aim of this study is to assess if C. avellana has an immune adjuvant effect. Human macrophages were pre-treated with hazelnut liquid extract, found to be rich in phenylpropanoids, and subsequently infected with Staphylococcus aureus. Based on the intracellular bacteria CFU reduction and on the treatment doses used, the donors were divided into High-Dose and Low-Dose-Responders. Expression profile for inflammatory and Iron metabolism genes, both for Peripheral Blood Mononuclear Cells and Macrophages, highlighted that Low-Dose-Responders came from a more pronounced pro-inflammatory milieu as compared with High-Dose-Responders. Blood test results revealed that Low-Dose-Responders had higher LDL C and Triglycerides and lower HDL C. Overall, our results suggest that the effect of the extract on Macrophage immune response is influenced by the intracellular inflammatory status of the donor.